Optimizing Soil Moisture Station Networks for Future Climates

Soil moisture is central to local climate on land. In situ soil moisture observations are vital for observing vegetation-relevant root-zone soil moisture. However, stations included in the International Soil Moisture Network are sparse in regions with strong land-atmosphere coupling. We apply a machine-learning-based procedure for informing future station placement using virtual soil moisture stations in future CMIP6 projections. Stations are placed where the climate is currently most under-represented. This strategy outperforms random station placement and station placement according to geographical distance. Doubling the current number of stations using this method alleviates the uneven global distribution of stations, increases the skill in the estimation of inter-annual variability and trends in dry-season soil moisture, and reduces its differences across climates in future projections. Stations are predominantly placed in tropical climates, especially when optimizing for drying trends. The results can inform future station placement to support climate change mitigation efforts.